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Title: CaCl 2 -Accelerated Hydration of Tricalcium Silicate: A STXM Study Combined with 29 Si MAS NMR

The effect of calcium chloride (CaCl 2 ) on tricalcium silicate (C 3 S) hydration was investigated by scanning transmission X-ray microscopy (STXM) with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra and 29 Si MAS NMR. STXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system. The Ca L 3,2 -edge NEXAFS spectra obtained by examining C 3 S hydration in the presence of CaCl 2 showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H), which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C 3 S. Based on the Ca L 3,2 -edge spectra and chemical component mapping, we concluded that CaCl 2 prefers to coexist with unhydrated C 3 S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl 2 increases the degree of silicate polymerization of C-S-H in agreement with the 29 Si CP/MAS NMR results, which show that the presence of CaCl 2 in hydrated C 3 S considerably accelerates the formation of middle groups ( Q 2 ) and branch sites ( Q 3 ) in the silicate chains of C-S-H gel at 1-day hydration.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [3]
  1. School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin 150090, China, Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720, USA
  2. School of Transportation Science and Engineering, Harbin Institute of Technology, Harbin 150090, China
  3. Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720, USA
  4. Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA 94720, USA, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamasaki, Noda, Chiba 278-8510, Japan
Publication Date:
OSTI Identifier:
1227339
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Journal of Nanomaterials
Additional Journal Information:
Journal Volume: 2015; Related Information: CHORUS Timestamp: 2016-07-27 06:21:35; Journal ID: ISSN 1687-4110
Publisher:
Hindawi Publishing Corporation
Sponsoring Org:
USDOE
Country of Publication:
Egypt
Language:
English